Really? I've seen it on Youtube before.
Maybe someone re-uploaded it, and maybe it's a better copy, but I don't think it's gonna get taken down. A lot of other Muppet specials are still up.
I mean, there are a lot of Muppet stuff up there, I think the only stuff that's stays up there is stuff that's not on DVD/Blu-Ray.

Fraggles Look for Jobs isn't up there?!
Yikes!! This is not good! Anyway, whenever you come across a great Muppet special, always download it, you just never know....
Also, it might just be Disney being nice, they might figure "Hey, you know what? We're not selling this anyway, so why take it down?" but of course, that doesn't really sound like Disney.

One of the members on here is the one who uploaded the special. I loved this special because you could totally see that Kermit had feelings for Piggy when she sang her song to him. And when Gonzo said "Kermit your starting to glow" I got goosebumps! And you can't argue that it was within a movie because the set up was just like TMS backstage stuff and all!